Numerical study on holdup of low-decontaminated MOX powder in proposed confinement box

In the Fast reactor Cycle Technology development (FaCT) project, the low-decontaminated MOX powder, which includes minor actinide components, is planned to be used for fuel fabrication material. Comparing to the present MOX powder produced by PUREX process, the high radiation background and decay heat of the new process would make the present remote-monitoring technologies difficult to apply nuclear material accounting. At the present, the MOX fabrication process is preliminarily reviewed as a feasibility study in the conceptual designing phase, and we have started to investigate an overall characteristic of nuclear material accounting of Pu in the proposed confinement box and to identify key issues for the future safeguards R and D. Although a possible accounting technology to meet the future regulatory criteria that would be developed by the IAEA is not appropriate to discuss from our developer side, we consider a possible safeguards alternative through this study. Flow field induced by a forced convection inside the box is numerically simulated to evaluate the MOX particle behavior. And a radiation field due to the spontaneous and induced neutrons emitted from Cm and Pu that are accumulated as the residuals in the box is calculated using PHITS code. Base on the numerical consideration, we will present the possibility of remote-monitoring techniques to apply to a future safeguards measure. (author)